1. Field of the Invention
The present invention relates to lithotripsy devices, and in particular to such devices combined with a means for locating the calculus to be disintegrated in the body of a patient.
2. Description of the Prior Art
A shock wave device for disintegrating a calculus in the human body is generally described, for example, in German OS No. 33 28 039. A shock wave tube is used as the shock wave source. The shock wave tube has an electrical coil, an insulating foil, and a copper membrane arranged in sequence. When a current pulse is applied to the coil, eddy currents are generated in the membrane, causing the membrane to be rapidly repelled from the coil. A shock wave is formed in the adjacent transmission medium, such as water. The shock wave is focussed by an acoustic lens having a focal point disposed in the calculus of the patient after a suitable positioning procedure. The calculus may be, for example, a kidney stone.
Locating the position of the calculus in the body of the patient is of great significance to the degree of therapeutic success, as well as for decreasing the load on the patient during therapy. The chances for successful therapy increase, and the load on the patient decrease, as the targeting becomes more precise. It is known to undertake such locating using x-ray devices. A disadvantage of such conventional locating means, however, is that the position of the calculus cannot be monitored during the complete shock wave treatment, because this would result in an undesireable x-radiation load on the patient. X-ray images are therefore recorded only from time to time during therapy to monitor the position of the calculus.
For continuously monitoring the calculus position, it is known to use an ultrasound system as the locating means. For example, German Patent No. 34 27 001 corresponding to U.S. Pat. No. 4,669,483 discloses a locating and positioning method wherein the calculus is located with an ultrasound oscillator, prescribed identification marks are set, and the calculus and the focal point of the shock wave system are subsequently mechanically brought into coincidence.
It is also known from German OS No. 31 19 295 corresponding to U.S. Pat. No. 4,526,168 to undertake locating of the calculus using the shock wave sour In the system described therein, the shock wave source is an arrangement of a plurality of piezo-electric transducer elements. This method, however, can be used only given shock wave sources wherein the shock wave pulse is produced using such piezo-electric elements.